Disarm device

ABSTRACT

A disarm device for use with a hitch arrangement on a working arm of a working machine, the device comprising a measurement device for measuring a property associated with the arm which can be used to determine whether or not a working implement carried by a working arm is sufficiently supported by a surface on to which it is to be released.

TECHNICAL FIELD

The present invention relates to a disarm device for use with a working machine hitch arrangement, the hitch and a working arm, especially, although not exclusively limited to, a disarm device for a quick—hitch arrangement on a working arm of an excavator, or backhoe loader or telescopic handler.

BACKGROUND OF THE INVENTION

Conventional working machines, such as used in the construction industry, agriculture, mining, earth moving, object handling and the like, for example a backhoe loader, comprise at least one working arm carrying a hitch or coupler arrangement which may be an at least partially automated hitch arrangement and which is configured for coupling to a working implement. The hitch arrangement typically comprises a hook for coupling to a pin of a working implement such that the hook extends around at least part of the pin. The hitch arrangement also typically comprises a further hook which is configured to receive a further pin of the working implement.

The hitch arrangement may be removable from the working arm and may be coupled to the working arm by an attachment arrangement which is also configured to couple a working implement to the working arm.

The hitch arrangement includes a closure arrangement for the further hook, the closure arrangement being moveable between a closed and an open position with respect to the further hook. When in the closed position, the further pin received by the further hook is prevented from leaving the further hook by the closure arrangement; when in the open position, the further pin received by the further hook is permitted to leave the further hook. The hook and the further hook are arranged such that the pin held by the hook is prevented from leaving the hook when the further pin is received by the further hook. Accordingly, the hitch arrangement can be used to secure a working implement thereto and the working implement can be released by actuation of the closure arrangement and movement of the hitch arrangement with respect to the working implement—to release the pin and further pin from the hook and further hook respectively.

The closure arrangement is driven between the open and closed positions by a closure driving arrangement which is typically a hydraulic, pneumatic or electrical (solenoid or motor) closure driving arrangement—although manual arrangements are also known. The closure driving arrangement is operated by an operator actuating a user operable control which is coupled to the closure driving arrangement.

It will be appreciated that if the closure arrangement of the hitch arrangement of the working arm is actuated to adopt the open position when the working arm is in some position, there is a risk that the working implement will fall out of the hitch arrangement in an undesired manner under the force of gravity.

In addition, the closure arrangement of the hitch arrangement of the working arm may be actuated to adopt the open position when the working arm is in a position in which there is no or little risk that the working implement falling out of the hitch arrangement in an undesired manner but the working arm may subsequently be moved to a position in which there is a risk that the working implement will fall out of the hitch arrangement in an undesired and potentially dangerous manner under the force of gravity.

Prior attempts to solve such problems include arrangements in which the closure arrangement of the hitch arrangement of the working arm is only actuable to adopt the open position when a hydraulic ram associated with the hitch arrangement is fully extended. However, this does not eliminate the risk of the working implement falling out of the hitch arrangement in an undesired and potentially dangerous manner under the force of gravity.

In another arrangement, a signal indicative of the orientation of a working implement secured to the hitch arrangement with respect to gravity is generated and a control module is configured to receive the signal and to perform a safety function in response to receipt of the signal such that the safety function is performed if the orientation of a working implement secured to the hitch arrangement with respect to gravity is an unpermitted orientation.

SUMMARY OF THE INVENTION

The provision of the sensors and the control module means that the working machine of the present invention is provided with a system that has the intelligence to prevent a working implement falling from the hitch due to the force of gravity in a range of positions. This advantage is achieved by detecting the actual orientation of the working implement rather than relying on a sensed position of an associated component, e.g. a hydraulic ram, of the working machine. Nevertheless, it is preferred to be more certain that the working implement is not suspended above the ground before releasing the implement from the working arm.

It is an object of the invention to provide an improved disarm device.

According to a first aspect of the invention there is provided a disarm device for use with a hitch arrangement on a working arm of a working machine, the device comprising a measurement device for measuring a property associated with the arm which can be used to determine whether or not a working implement carried by a working arm is sufficiently supported by a surface on to which it is to be released.

In that way the disarm device checks that the working implement is not suspended above the ground, thereby reducing the risk that the working implement is dropped when released.

The disarm device may be separate from the arm, integrated onto the hitch arrangement, integrated onto the arm or carried elsewhere on the machine. The device may be an integral feature or it may be retro fitted.

According to a second aspect of the invention there is provided a working arm having a hitch arrangement by which a working implement is attachable to the arm, a measurement device for measuring a property associated with the arm which can be used to determine whether or not a working implement carried by the arm is sufficiently supported by a surface onto which the working implement is to be released.

The following features may form part of either the first or second aspects of the invention above. A measurement device preferably provides a signal to a controller which determines whether or not the working implement carried by the working arm is sufficiently supported by a surface onto which it is to be released based on the measured property. The controller may be a dedicated microprocessor for the disarm device or a computer running various functions on a working machine. The controller is preferably configured to receive a signal from the measurement device indicative of the property measured prior to processing the signal to determine whether or not the working implement is sufficiently supported by a surface on which it is to be released and, in the event that the implement is not sufficiently supported by a surface on which it is to be released, to perform a safety function.

Where the working arm is driven by hydraulics, the measurement device may be a pressure sensor. In such a case, the controller determines whether or not the working implement carried by the working arm is sufficiently supported by a surface on which it is to be released by comparing the sensed pressure with a pressure threshold level. The measurement device may be a load sensor on the hitch arrangement for measuring a load on the hitch. In such a case, the controller determines whether or not the working implement carried by a working arm is sufficiently supported by a surface on which it is to be released by comparing the measured load on the hitch with a load threshold level. The load sensor may be a strain gauge or other load sensing means. The disarm device according to the first aspect or the working arm in accordance with the second aspect may employ both a pressure sensor on the arm hydraulics and a load sensor on the hitch arrangement and the controller may use both the pressure signal and load signal to determine whether or not a working implement carried by a working arm is sufficiently supported by a surface onto which it is to be released. Optionally, the disarm device of the first aspect or the working arm of the second aspect may further include one or more sensors configured to determine an orientation of a working implement secured to the hitch arrangement and to output a signal indicative of the orientation of a working implement secured to the hitch arrangement with respect to gravity, the controller then being configured to receive the signal from the one or more sensors and to perform a safety function in response to receipt of the signal such that the safety function is performed if the orientation of a working implement secured to the hitch arrangement with a respect to gravity is an unpermitted orientation. Preferably, the disarm device of the first aspect or the working arm of the second aspect includes a sensor to determine the angle of the working arm. In some extreme configurations of the working arm, some load sensing arrangements may give a false reading that the working implement is supported on the ground when, in fact, it remains suspended. The arm angle sensor acts as a check to prevent inadvertent release. The controller in the first or second aspect in such a case, uses a signal from the measurement device measuring the property associated with the arm to determine whether or not a working implement carried by a working arm is sufficiently supported by a surface on which it is to be released in combination with a signal from the one or more sensors configured to determine an orientation of a working implement attached to the hitch arrangement indicative of orientation of a working implement.

The working arm may be an excavator arm, a backhoe arm or a telescopic handler arm. The working implement may be a bucket, fork lift assembly or any other appropriate tool.

The safety function preferably comprises the controller either disarming or locking the hitch arrangement to prevent inadvertent release of the working implement secured to the hitch arrangement. The safety function may, alternatively or additionally, comprise providing an indication to the user either visually, audibly or both visually and audibly, as required by pertinent safety standards.

According to a third aspect of the invention there is provided a working machine equipped with a disarm device according to the first aspect of the invention or a working arm according to the second aspect of the invention optionally including any of the preferred features mentioned above.

According to a fourth aspect of the invention there is provided a method of operating a hitch arrangement on a working arm of a working machine comprising the steps of:

providing a working arm having a hitch arrangement, providing a working implement attached to the arm by means of the hitch arrangement, measuring a property associated with the arm, using the measured property to determine whether or not a working implement carried by the working arm is sufficiently supported by a surface on which it is to be released, and, on determining that the tool is sufficiently supported, permitting operation of the hitch arrangement to effect release of the tool.

According to a fifth aspect of the invention there is provided a method of operating a hitch arrangement on a working arm comprising steps of providing a working arm having a hitch arrangement, providing a working implement attached to the working arm by means of the hitch arrangement, measuring a property associated with the arm, using the measured property to determine whether or not a working implement carried by the working arm is sufficiently supported by a surface on which it is to be released, and, on determining that the tool is not sufficiently supported, preventing operation of the hitch arrangement so as to prevent release of the working implement.

In the fourth aspect the hitch arrangement is normally disarmed and is armed when the method determines that the tool is sufficiently supported whereas in the fifth aspect the hitch arrangement is normally armed and is disarmed when the method determines that the working implement is not sufficiently supported.

The following features characterise the methods of the fourth and fifth aspects. The step of measuring a property associated with the arm is preferably measuring the pressure in a hydraulic circuit used to drive the arm. In such a case, the step of using the measured property to determine whether or not the tool carried by the arm is sufficiently supported by a surface on which it is to be released involves comparing the measured pressure with a pressure threshold level. Alternatively or additionally the step of measuring a property associated with the arm comprises measuring a load carried by the hitch arrangement. In such a case, the step of using the measured property to determine whether or not the working implement carried by the arm is sufficiently supported by a surface on which it is to be released comprises comparing the measured load with a load threshold level. Optionally, both pressure and load are measured and the measured pressure and measured load are respectively compared against pressure threshold level and lead threshold level. Both aspects of the invention may further comprise the step of determining an orientation of a working implement secured to the hitch arrangement and determining the orientation of a working implement secured to the hitch arrangement with respect to gravity and determining whether or not the orientation of a working implement secured to the hitch arrangement with respect to gravity is an unpermitted orientation.

In a preferred embodiment of the fourth aspect of the invention the method comprises the further step of providing indication to the user that operation of the hitch arrangement is permitted. In a preferred embodiment of the fifth aspect of the invention the method further comprises the step of indicating to the user that the operation of the hitch arrangement is not permitted.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a side elevation of a backhoe loader working machine having a disarm device, a hitch arrangement and a working arm in accordance with the first to third aspects of the invention and employing the fourth and fifth aspects of the invention

FIG. 2 is a side elevation of an excavator working machine also embodying the first to fifth aspects of the invention.

FIGS. 3 and 4 are side views of a telescopic handler working machine embodying the first to fifth aspects of the invention, and

FIGS. 5 a, b and c are flowcharts showing methods of operating a working arm in accordance with the fourth and fifth aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

A working machine 1, such as a backhoe loader (as shown in FIG. 1) or an excavator (as shown in FIG. 2) includes a ground engaging arrangement 2 comprising (in FIG. 1) two or more pairs of wheels 3 mounted on respective axles, wherein at least one of the axles is coupled to a driving arrangement which drives rotational movement of at least one of the pairs of wheels 3 or two or more endless tracks (see FIG. 2).

The two or more pairs of wheels 3 or endless tracks are arranged to engage a ground surface 4 and rotational movement of the or each pair of wheels 3 or tracks causes movement of the working machine 1 across the ground surface 4.

In FIG. 1 the ground engaging arrangement 2 carries a main body 5 of the machine 1 and a first working arm 6 extends forwardly from the main body 5. A proximal end 61 of the first working arm 6 is coupled to the main body 5 and a distal end 62 of the first working arm 6 is configured for connection, by a first hitch arrangement 7, to a first working implement 8.

In FIG. 1 a second working arm 9 is provided which extends from the main body 5. In FIG. 2 the second working arm 9 is the only working arm on the machine. The second working arm 9 may extend rearwardly (see FIG. 1) or forwardly (see FIG. 2). The second working arm 9 comprises a boom 91 connected to a proximal end 911 to the main body 5 by a king post or other pivotal arrangement. A distal end 912 of the boom 91 is connected to a proximal end 921 of a dipper arm 92 by a pivotal arrangement. A distal end 922 of the dipper arm 92 is configured for connection, by a second hitch arrangement 10, to a second working implement 11.

It will be appreciated that embodiments of the present invention may include a working machine 1 with only a second working arm 10 and no first working arm 11 (see FIG. 2 for example).

The first and/or second 10 hitch arrangements may be part of their respective working arm 6,9 or may be removably attached thereto.

The driving arrangement or engine of the machine 1 is housed in the main body 5 of the machine 1 which includes an operator cab 12. The operator cab 12 houses a plurality of user operable controls 13, the actuation of which control the operation of parts of the machine 1.

The first 6 and second 9 working arms are coupled to respective hydraulic driving arrangements 63,93 which are configured to drive movement of the first 6 and second 9 working arms with respect to the main body 5 of the machine 1. The hydraulic driving arrangements 63,93 may also drive movement of the hitch arrangements 7, 10 and/or working implements 8,11 with respect to the working arms 6,9. The hydraulic driving arrangement 63 coupled to the first working arm 6 in FIG. 1 comprises a bucket ram 631 and a boom ram 632.

The hydraulic driving arrangement 93 (see FIGS. 1 and 2) coupled to the second working arm 9 includes a first (boom) hydraulic ram 932 (see FIG. 2) configured to drive rotational movement of the boom 91 with respect to the main body 5 of the machine 1 between a first and a second boom position. The hydraulic driving arrangement 93 coupled to the second working arm 9 includes a second hydraulic ram 933 configured to drive rotational movement of the dipper arm 92 with respect to the boom 91 between a first and a second dipper arm position. The hydraulic driving arrangement 93 coupled to the second working arm 9 also includes a third hydraulic ram 93 (sometimes known as a bucket ram 931) which is configured to drive rotational movement of the second hitch arrangement 10 and any working implement coupled thereto (such as the second working implement 11) with respect to the dipper arm 92 between a first and a second working implement position (the first working implement position being with the third hydraulic ram 931 fully retracted and the second working implement position being with the third hydraulic ram 931 fully extended). The third hydraulic ram 931 is configured to drive rotational movement of part of the second hitch arrangement 10 and any working implement coupled thereto with respect to the dipper arm 92 between the first and the second working implement position.

The working arm 9 may be a triple articulated boom arm.

FIGS. 3 and 4 show a working machine 1 in the form of a telescopic handler. The machine 1 is supported by two pairs of wheels 3, as in the FIG. 1 machine, which engage the ground surface 4. The machine 1 has a main body 5 mounting an operator cab 12 and a telescopic working arm 17. The working arm 17 is pivotally mounted to the body 5 at the rear of the body and can be lifted about that pivot by a hydraulically driven boom cylinder (not shown) to raise the working arm 17. The arm 17 can be telescopically extended by means of a hydraulic drive 173. A hitch arrangement 7 similar to that in FIG. 1 is mounted to the free end of the arm 17. The hitch arrangement 7 may be used to mount a working implement 8, in this case, forks (part shown).

One or both of the first 7 and second 10 hitch arrangements may be at least partially automated hitch arrangements 7,10.

The hitch arrangements 7, 10 comprise a hitch attachment arrangement which is configured to be coupled to a corresponding working implement attachment arrangement of a working implement 8,11. Accordingly, the hitch attachment arrangement and the working implement attachment arrangement are configured to cooperate in order to mate with each other. In an embodiment, the hitch attachment arrangement comprises at least one first hook for coupling to one or more first pins of a working implement attachment arrangement of a working implement 8,11 such that the or each first hook extends around at least part of the circumference of one of the or each of the first pins.

One or more second hooks or recesses are provided which are each configured to receive one or more second pins of the working implement 8,11.

The working implement attachment arrangement comprises one or more hooks or recesses configured to receive one or more pins of the hitch attachment arrangement.

The working implement attachment arrangement comprises one or more hooks or recesses and one or more pins, the or each hook or recess and the or each pin being configured to receive or be received by a respective hook or recess, or pin of the hitch attachment arrangement.

The one or more second hooks or recesses may be one or more second hooks or recesses of the working implement attachment arrangement or the hitch attachment arrangement. The one or more second pins may be one or more second pins of the working implement attachment arrangement or the hitch attachment arrangement.

A closure arrangement is provided for the or each second hook or recess, the closure arrangement being moveable between a closed and an open position.

When in the closed position, the or each second pin received by the or each second hook or recess is prevented from leaving the or each second hook or recess by the closure arrangement. When in the open position, the or each second pin received by the or each second hook or recess is permitted to leave the second hook or recess. The or each first hook and the or each second hook or recess are arranged such that the or each first pin held by the or each first hook is prevented from leaving the or each first hook when the or each second pin is received by the or each second hook or recess.

The closure arrangement may comprise one or more moveable bolts which are axially moveable with respect to the or each second hook or recess. The closure arrangement may comprise one or more claws which are rotationally moveable with respect to the or each second hook or recess. It will be appreciated that, in embodiments, the closure arrangement may form part of the hitch attachment arrangement or the working implement attachment arrangement. The closure arrangement need not be provided in combination with a second hook or recess but could be provided in combination with other elements of the attachment arrangements. In an embodiment, a closure arrangement is provided in relation to the first hook or recess and/or the second hook or recess. Reference to a closure arrangement herein refers to the closure arrangement or a plurality of arrangements of a hitch attachment arrangement or working implement attachment arrangement.

Accordingly, the hitch arrangements 7, 10 can be used to secure respective working implements 8,11 thereto and the working implements 8,11 can be released by actuation of the closure arrangement of the relevant hitch arrangement 7,10 and movement of the relevant hitch arrangement 7,10 with respect to the working implement 8,11—to move the pins out of the first hook and the second hook or recess (for example).

The hitch arrangements 7,10 may include one or more locking pins or other locking arrangements (not shown) which are automatically or manually moved into a locked position (from an unlocked position) when the closure arrangement is in the closed position. Similarly, the one or more locking pins or other locking arrangements may be moved from the locked position to the unlocked position when it is desired to move the closure arrangement to the open position. The or each locking pin or other locking arrangements may be arranged such that, in the locked position, movement of the closure arrangement to the open position is substantially prevented by the or each locking pin or other locking arrangement. The or each locking pin or other locking arrangement is, therefore, a safety device which helps to reduce the risk of release of a working implement 8,11 from a hitch arrangement 7,10 at an undesired juncture by the unintentional movement of the closure arrangement to the open position. A pneumatic or hydraulic or electric driving arrangement may be provided for the or each locking pin or other locking arrangements to move the locking pin or other locking arrangement between the locked and unlocked positions (a single driving arrangement may be provided for multiple locking pins or other locking arrangements). A user operable control 13 may be provided, the actuation of which by a user causes movement of the or each locking pin or other locking arrangement between the locked and unlocked positions.

The closure arrangement is preferably driven between the open and closed positions by a closure driving arrangement which may be a hydraulic or pneumatic or electric driving arrangement.

The closure driving arrangement may be moved by an operator actuating a user operable control 13 which may be provided in the operator cab 12 of the machine 1—the user operable control 13 being coupled to the closure driving arrangement and configured to cause movement thereof between the open and closed positions. One or more closure driving arrangements may be provided in embodiments of the invention. A single closure arrangement may be provided for multiple second hooks or recesses and/or multiple second pins.

As will be understood, therefore, a user can attach or detach the second working implement 11 to or from the second hitch arrangement 10 by controlling the operation of the closure arrangement (and the locking pin or other locking arrangement if provided).

It will be appreciated that a multitude of different hitch arrangements are possible and are compatible with embodiments of the present invention. The above examples are merely some examples of suitable hitch arrangement. In some working arm arrangements there may be a two serially arranged hitch arrangements on the same arm, the first to mount, e.g. a rotary manipulator, which carries the second hitch to which the working implement is mounted. In such a case, the disarm device is associated with a pre-selected one of the two hitch arrangements. Alternatively, the control may be used to operate either one of the two hitch arrangements at a time and, in such a case, the disarm device functions in relation to the operated hitch.

The machines 1 in FIGS. 1 and 2 are equipped with a pressure sensor 20 on the hydraulic circuits 63, 93 which drive the arms 6, 9. The pressure sensor 20 measures the pressure in the respective hydraulic circuit 63,93 and outputs a pressure signal to a controller 22. The controller 22 can be a dedicated microprocessor or it may be an onboard computer which controls multiple functions of the machine 1. The sensor 20 may output the signal by wire or wirelessly.

In FIG. 1, one sensor is provided for the whole hydraulic system 63,93 but it is also possible to provide dedicated sensors for each of the circuits 63,93 for the respective arms 6, 9 which output a pressure signal indicative of the pressure in the respective circuit. Such dedicated sensors may output their signals to a single controller or to respective dedicated controllers. Specifically, the pressure sensor 20 measures the pressure in the respective boom cylinder 632, 932.

The machine 1 in FIG. 3 is provided with a load sensor 24, such as a strain gauge on the hitch arrangement 7 which is arranged to output a signal indicative of the load on the hitch arrangement. The load signal is passed by wire or wirelessly to controller 22 on the machine 1. In this case, the controller 22 is in the cab 12 but may, as with FIGS. 1 and 2, be a dedicated controller or onboard computer. The machine 1 in FIG. 3 is optionally provided with a pressure sensor 20 on the boom cylinder of the hydraulic circuit 173 as in the machines of FIGS. 1 and 2 which outputs a pressure signal to the controller 22.

The machines 1 in FIGS. 1 and 2 may optionally be provided with respective load sensors 24 on the hitch arrangement 7, 10.

When the operator of the machine 1 in FIG. 1 or FIG. 2 wishes to decouple the working implement 8, and 10 from the hitch 7, 9, the operator activates the closure arrangement of the hitch arrangement.

The controller 22 receives the pressure signal from the pressure sensor on the hydraulic circuit 63, 93 measuring pressure in the respective boom cylinder 632, 932. If the pressure in the cylinder exceeds a threshold level then it indicates that the working implement 8, 10 is suspended above the ground as the arm is bearing the weight of the implement. If the implement is supported on the ground surface 4 then the pressure in the cylinder will be below the threshold level. If the pressure is above the threshold then the controller either disarms the closure arrangement or actuates a lock, preventing decoupling. If the pressure is below the threshold, the controller arms the closure arrangement or does not actuate a lock, allowing the operator to decouple the working implement 8, 10 from the arm (see FIG. 5 a).

The first 6 and second 9 working arms or the telescopic working arm 17 and their respective hydraulic driving arrangements 63,93, 173 are such that each arm 6,9, 17 can adopt a number of different positions with respect to the main body 5 of the machine 1 during operation. Each arm 6, 9, 17,15 is optionally equipped with a sensor 16 which outputs a signal indicative of the orientation either of the arm or of the working implement 7, 10 with respect to gravity.

In an embodiment, the one or more sensors 16 are configured to determine an orientation of a working implement 8, 10 secured to the hitch arrangement 9, 11 and the hitch arrangement 11 with respect to gravity and to output a signal indicative of the orientation of the working implement 8, 10 and the hitch arrangement 9, 11 with respect to gravity. According to embodiments, the one or more sensors 16 may each comprise one or more Hall effect sensors and/or one or more Reed switches and/or one or more mercury switches and/or one or more proximity sensors, or the like.

This orientation or tilt sensor can be used in addition to the pressure or load sensor to disarm/lock or arm/unlock the hitch (see FIG. 5 b).

FIG. 5 c illustrates a detailed method of operating, e.g. the machine 1 of FIG. 1. When the operator wishes to decouple the working implement 8 from the hitch 7, he presses a hitch button in the cab. This generates a confirmation query on a display, in cab, prompting the user to press a further control enabling the hitch hydraulics. The tilt sensor then outputs a signal to the controller 22 which confirms the orientation of the working implement and if it is in an acceptable orientation allows the procedure to go forward. If the orientation of the implement is not acceptable then the controller sends an appropriate error message to the in cab display and the procedure reverts to the start point.

After orientation approval, the pressure sensor 20 and/or load sensor 24 provide a signal to the controller 22 which compares the or each signal to a respective threshold level to determine whether or not the working implement is sufficiently supported on, e.g. the ground. If it is sufficiently supported then the hitch arrangement 7 is armed and pressing the hitch button will result in decoupling of the working implement in accordance with machine specific operating sequence for instance; hydraulically actuated hitch types may require system pressure to be raised. If not then the hitch arrangement remains disarmed or locked preventing decoupling and a “ground tool” message is displayed.

On recoupling a working implement to the hitch, the hitch is re-locked and the machine reverts to its normal mode, deactivating the hitch hydraulics.

On cycling the power to the machine controller (e.g. switching off engine or isolating controls) the hitch will revert to its normal mode, deactivating the hitch hydraulics.

It will be appreciated that, as used herein, a “signal” refers to the transmission of information and this may be achieved in an electrical system in the change of a voltage and/or current or in a fluid system (e.g. hydraulic or pneumatic) in the change of a fluid flow or pressure.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof. 

1. A disarm device for use with a hitch arrangement on a working arm of a working machine, the device comprising a measurement device for measuring a property associated with the arm which can be used to determine whether or not a working implement carried by a working arm is sufficiently supported by a surface on to which it is to be released.
 2. A disarm device according to claim 1, in which the measurement device provides a signal to a controller which determines whether or not the working implement carried by the working arm is sufficiently supported by a surface onto which it is to be released based on the measured property.
 3. A disarm device according to claim 2, in which the controller is configured to receive a signal from the measurement device indicative of the property measured prior to processing the signal to determine whether or not the working implement is sufficiently supported by a surface on which it is to be released and, in the event that the implement is not sufficiently supported by a surface on which it is to be released, to perform a safety function.
 4. A disarm device according to claim 1, in which, where the working arm is driven by hydraulics, the measurement device is a pressure sensor.
 5. A disarm device according to claim 4, in which the controller determines whether or not the working implement carried by the working arm is sufficiently supported by a surface on which it is to be released by comparing the sensed pressure with a pressure threshold level.
 6. A disarm device according to claim 1, in which the measurement device is a load sensor on the hitch arrangement for measuring a load on the hitch.
 7. A disarm device according to claim 6, in which the controller determines whether or not the working implement carried by a working arm is sufficiently supported by a surface on which it is to be released by comparing the measured load on the hitch with a load threshold level.
 8. A disarm device according to claim 1, further comprising one or more sensors configured to determine an orientation of a working implement secured to the hitch arrangement and to output a signal indicative of the orientation of a working arm or working implement secured to the hitch arrangement with respect to gravity, the controller then being configured to receive the signal from the one or more sensors and to perform a safety function in response to receipt of the signal such that the safety function is performed if the orientation of the working arm or working implement secured to the hitch arrangement with a respect to gravity is an unpermitted orientation.
 9. A disarm device according to claim 8, in which the controller uses a signal from the measurement device measuring the property associated with the arm to determine whether or not a working implement carried by a working arm is sufficiently supported by a surface on which it is to be released in combination with a signal from the one or more sensors configured to determine an orientation of a working arm or working implement attached to the hitch arrangement indicative of orientation of a working implement.
 10. A disarm device according to claim 3, in which the safety function comprises the controller either disarming or locking the hitch arrangement to prevent inadvertent release of the working implement secured to the hitch arrangement.
 11. A disarm device according to claim 3, the safety function comprises providing an indication to the user.
 12. A method of operating a hitch arrangement on a working arm of a working machine comprising the steps of: providing a working arm having a hitch arrangement, providing a working implement attached to the arm by means of the hitch arrangement, measuring a property associated with the arm, using the measured property to determine whether or not a working implement carried by the working arm is sufficiently supported by a surface on which it is to be released, and, on determining that the tool is sufficiently supported, permitting operation of the hitch arrangement to effect release of the tool.
 13. A method of operating a hitch arrangement on a working arm comprising steps of: providing a working arm having a hitch arrangement, providing a working implement attached to the working arm by means of the hitch arrangement, measuring a property associated with the arm, using the measured property to determine whether or not a working implement carried by the working arm is sufficiently supported by a surface on which it is to be released, and, on determining that the tool is not sufficiently supported, preventing operation of the hitch arrangement so as to prevent release of the working implement.
 14. A method of operating a hitch arrangement according to claim 13, in which the step of measuring a property associated with the arm is measuring the pressure in a hydraulic circuit used to drive the arm.
 15. A method of operating a hitch arrangement according to claim 14, in which the step of using the measured property to determine whether or not the tool carried by the arm is sufficiently supported by a surface on which it is to be released involves comparing the measured pressure with a pressure threshold level.
 16. A method of operating a hitch arrangement according to claim 13, in which the step of measuring a property associated with the arm comprises measuring a load carried by the hitch arrangement.
 17. A method of operating a hitch arrangement according to claim 16, in which the step of using the measured property to determine whether or not the working implement carried by the arm is sufficiently supported by a surface on which it is to be released comprises comparing the measured load with a load threshold level.
 18. A method of operating a hitch arrangement according to claim 13, further comprising the step of determining an orientation of a working arm or a working implement secured to the hitch arrangement and determining the orientation of a working arm or a working implement secured to the hitch arrangement with respect to gravity and determining whether or not the orientation of a working arm or a working implement secured to the hitch arrangement with respect to gravity is an unpermitted orientation.
 19. A method of operating a hitch arrangement according to claim 13, the method further comprising the step of indicating to the user that the operation of the hitch arrangement is not permitted. 